Lon Williamson <[EMAIL PROTECTED]> wrote: >Why a new physical mount, then? Surely they could do the electronics >with a serial protocol, which would require, at minimum, >ground, power, and signal: three contacts.
I've thought of that too, but apparently they don't use a serial protocol - at least judging by the number of contacts used. I have no idea why. Anyone know the pinout designations for EOS mount? >As I understand it, the EOS mount is much different >mechanically from the old FD mount. Wider throat. >Are other factors at work? Well, a wider throat allows them to put the electronic contacts at the base of the lens extending radially, rather than using the axial contact orientation that Pentax uses. It also gives more freedom in lens design because the rearmost element can be larger - like a 50mm f/1.0, for example. -- Mark Roberts Photography and writing www.robertstech.com

